Made ready rubber printing plates



Oct. 26, 1965 G. S. BRAZNELL ETAL MADE READY RUBBER PRINTING PLATESUnited States Patent O MADE READY RUBBER PRINTING PLATES 'George StuartBraznell, Frontenac, and Ralph E. Mc- Ilvaney, St. Louis County, Mo.,assignors to Braco Engraving Company, St. Louis, Mo., a corporation ofMissouri Original application Mar. 19, 1962, Ser. No. 180,472, nowPatent No. 3,103,168, dated Sept. 9, 1963. Divided andv this applicationMay 16, 1963, Ser. No. 280,854

2 Claims. (Cl. 101-379) This invention relates to rubber printingplates, and more particularly to what may 'be referred to as a madereadyrubber printing plate.

This application is a division of our copending application Serial No.180,472, tiled March 19, 1962, and now U.S. Patent 3,103,168, issuedSeptember 9, 1963, entitled Printing Plates. l It will lbe understoodthat a rubber printing plate' essentially comprises a rubber platehaving on one face thereof -a pattern in relief -of the matter which isto be printed by means of the plate. When a pattern includes both largeprinting areas and small printing areas (such as fine lines or dots, forexample), it is usually necessary in order to obtain a proper impressionin the printing operation that provision lbe made for applying lesspressure on the small areas than the large areas, otherwise, lifsuiiicient pressure is applied for proper impression of the large areas,the small areas will be undesirably distorted. Heretofore variousexpedients have been used for making ready to provide suchdifferentiation in pressure, but these have usually involved operationssubsequent to formation of the rubber printing plate, and have involvedprocedures making accurately controlled differentiation in amount andlocation of pressure diticult to obtain. Ac-cordingly, amon-g theseveral objects of this invention may be noted the .provision of rubberprinting plates which are made ready (i.e., formed so as to provide forpressure differentiation between large and small .printing areas) duringthe production of the plates; and the provision of such plates which areeconomical to make and which provide accurate, built-in make-readycontrol. Other objects and features will be in part apparent and in partpointed out hereinafter.

The invention accordingly comprises the construction hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the `accompanying drawings, in which one of Various possibleembodiments lof the invention is illustrated,

FIG. 1 is a plan of a so-called master metal engraving;

FIG. 2 is a section on line 2-2 of FIG. 1;' v

FIG. 3 is a view similar to FIG. 2 showing how a so-called matrix ismade using the master engraving;

FIG. 4 is `a plan of the matrix;

FIG. 5 is a half-section in perspective of the FIG. 4 matrix;

FIG. 6 is a view of a so-called stencil sheet used in making a plate;

FIG. 7 is -a section showing -certain initial steps in the formation ofa rubber printing plate of this invention, using the matrix of FIGS. 4and 5 and the stencil sheet of FIG. 6;

FIG. 8 is a view of the printing face of the completed rubber printingplate;

FIG. 9 is a view of the other face (or back face) of the -completedrubber printing plate; and,

FIG. 10 is a half-section in perspective of the rubber printing plate ofFIGS. 8 and 9.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawmgs.

Referring to FIGS. 1 and 2 of the drawings, there is JCC indicated at `1what is referred to as a master engraving. As shown, this consists of arectangular metal plate, for example, which has one yface routed out asindicated at 3 to provide Ia desired printing pattern in relief, and aperipheral retaining wall 5 all around the plate. For purposes ofsimplified illustration, the printing pattern is shown as comprising tworelatively large printing areas, a square area 7 and a circular .area 9,and two relatively small printing areas, a fine-line area 11 and a dot13. This is illustrati-ve of conventional printing patterns which willinclude designs, trademarks, etc. The master engraving 1 is made vinwell-known conventional manner. The routing at 3 may be uniform indep-th throughout, corresponding to the thickness in relief desired forthe .printing areas on the printing face of the ru'bber printing plateto be made. The master engraving -1 is also shown .as formed withgrooves as indicated at 15 and 17 for forming centering lines 15a and17a (see FIGS. 4 and 5) in a matrix 19 (see FIGS. 4 and 5) to be madeusing the master engraving.

As shown in FIG. 3, the matrix is made using master eng-raving 1A inconventional manner by packing a thermosetting resin powder as indicatedat 21 into the routed cavity 3 in the master engraving, and covering thefaces of peripheral wall -5 and of areas 7, 9, 11 and 13 with thispowder to a predetermined depth. The powder may be a phenol-formaldehyderesin powder such as sold :under the trade designation Bakeliteconventionally used for making such matrices. A plate 23 ofthermosetting resin is applied over the powder. This plate may be aplate of phenol-formaldehyde resin such as sold under thetradedesignation Bakelite conventionally used for making such matrices. Itwill be understood that a parting compound will usually be applied tothe master engraving to enable the matrix to be stripped from theengraving. -Heat and pressure are applied to set and cure the resinpowder and bond it to plate 23, thereby to form a matrix 19 havingimpressions in reverse of relief of the printing areas 7, 9, 11 and 13of the master engraving. Referring to FIGS. 4 and 5, the impressions orcavities in the matrix 19 are respectively designated 7a, 9a, 11a and13a. By reason of the provision lof gnooves 15 and 17 in the masterengraving, lcentering lines 15a and 17a are formed as ridges on thematrix 19. FIGS. 4 and 5 show the matrix 19 stripped from the masterengraving 1.

As shown in FIG. 6, a so-called stencil sheet 25 is prepared havingopenings'7b and 9b corresponding in outline t-o the large areas 7 and 9of the master engraving 1 `and to the large areas 7a and 9a of thematrix 19, but Without any openings corresponding to small areas 11 and13. This sheet may be made of paper, sheet metal, or any other suitablematerial, and may be easily and accurately prepared simply by taking anink impression (a proof) on the stencil sheet off the master engraving1, then cutting out the areas printed on the sheet by contact with inkon .areas 7 and 9 of the master engraving. Centering lines 15b Aand 17bare marked on the stencil sheet, being accurately located thereonrelative to openings 7b and 9b from grooves 15 and 17 of the masterengraving.

As shown in FIG. 7, strips of unvulcanized rubber R are placed Iin thecavities 7a and 9a of the matrix, and over these cavities and otherportions of the matrix. Strips of unvulcanized rubber may also be placedover cavities 11a and 13a. A backing plate 27 is applied over rubber Ron the matrix. This backing plate 27, as appears in FIG. 7, may consistof a piece of fabric 29 having layers 31 and 33 of unvulcanized rubberon both faces thereof. Layer 31 is shown as thicker than layer 33, andlayer 31 is applied face down over rubber R on the matrix. It will beunderstood that a suitable parting material is applied to the matrixprior to application of rubber R and the backing plate 27. The rubberused at R and in plate 27 may have a durometer in the range from 20-80,.for example. Also as shown in FIG. 7, stencil sheet 25 is applied overthe backing plate 27, and is centered by registering lines 15b and 17bon the stencil sheet with lines 15a and 17a on the matrix so thatopenings 7b and 9b in the stencil sheet register at least approximately(if not perfectly) with cavities 7a and 9a in the matrix.

Then, the assembly of the matrix 19, rubber R, backing plate 27 andstencil sheet 25 is placed in a vulcanizing press, and heat and pressureare applied to cause filling of the cavities 7a, 9a, 11a and 13a in thematrix with rubber (from strips R, possibly also some rubber from layer31 of the backing plate), also to cause iilling of the openings 7b and9b of the stencil sheet with rubber from layer 33 of the backing plate,bonding of the rubber in the cavities of the matrix with the backingplate, and vulcanization of the rubber. It will be understood that thepressure causes squeeze-out of rubber from layer 33 into openings 7b and9b of the stencil sheet. This results in formation of the rubberprinting plate 35 shown stripped from the matrix in FIGS. 8-10, and withstencil sheet 25 removed, having the printing pattern comprisingprinting areas 7c, 9c, 11c and 13c (corresponding toareas 7, 9, 11 and13 of the master engraving) on its printing face (see FIGS. 8 and 10),and integral raised areas 7d and 9d on its other face (sec FIGS. 8 and9). Areas 7d and 9d correspond in outline to and are at leastapproximately in register with areas 7c and 9c. The faces of areas 7dand 9d are oiset from the back face cf plate 35 by an amount equal tothe thickness of the stencil sheet 25, and the amount of this offset maybe made as desired by using a stencil sheet of appropriate thickness.When the plate 35 is used on the printing cylinder of a printing press,for example, raised areas 7d and 9d eiect impression of ink on the workover areas 7c and 9c at higher pressure than over areas 11c and 13e (thelatter not being backed by any raised areas). The differentiation inpressure may be accurately controlled in amount by suitable preselectionof the thickness of the stencil sheet to determine the thickness ofraised areas 7d and 9d and is accurately controlled as to location aswill be evident. v

It will be understood that a rubber printing plate may be made inaccordance with the invention with raised areas of different thicknesson the back of the plate by using a plurality of appropriate stencilsheets of different thickness to provide the desired differentiation inthickness of the raised areas. In this manner, variable pressure may beobtained on dierent printing areas of the same plate for properimpression of all the printing areas.

In view of the above, it will be seen that the several objectsy of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A made ready printing plate of an elastomeric material having aprinting face and a generally at back face, the printing face having aprinting pattern in relief with all printing areas in the finished platebeing of substantially the same relief, the printing pattern comprisingrst and second printing areas, the rst printing area being relativelylarge and the second printing area being relatively small, the back faceof the plate having an integral area in relief corresponding generallyin outline to and approximately registering with said first relativelylarge printing area on the printing face, the area on the back facecorresponding to and registering with the second relatively smallprinting area being generally at with the remainder of said back face.

2. A made ready printing plate of an elastomeric material having aprinting face and a generally flat back face, the printing face havingaprinting pattern in relief with all printing areas in the finishedplate being of substantially the same relief, the printing patterncomprising relatively large printing areas and relatively small printingareas, the back face of the plate having integral areas in reliefcorresponding generally in outline to and approximately registering withsaid large printing areas on the printing face, the areas on the backface corresponding to and registering with the small printing areasbeing generally at with the remainder of said back face.

References Cited by the Examiner UNITED STATES PATENTS 952,312 3/10Droitcour lOl-401.3 1,219,472 3/ 17 Martinsen lOl-401.3 1,852,115 4/32Haggerty et al. lOl-401.3 2,088,399 7/37 Gibson lOl-401.3 2,863,00012/58V Hell alOl-426 OTHER REFERENCES Apps: Printing Ink Technology.Leonard Hill Limited, London, lst ed., pub. 1958. vTP49A6C-3 (page 391).

Flexography: Principles and Practices, Flexographic TechnicalAssociation, Inc., copyright 1962. Z 2441-15 (pages 16, 48-49).

DAVID KLEIN, Primary Examiner. WILLIAM B. PENN, Examiner.

1. A MADE READY PRINTING PLATE OF AN ELASTOMERIC MATERIAL HAVING APRINTING FACE AND A GENERALLY FLAT BACK FACE, THE PRINTING FACE HAVING APRINGINT PATTERN IN RELIEF WITH ALL PRINTING AREAS IN THE FINISHED PLATEBEING OF SUBSTANTIALLY THE SAME RELIEF, THE PRINGINT PATTERN COMPRISINGFIRST AND SECOND PRINTING AREAS, THE FIRST PRINGINT AREA BEINGRELATIVELY LARGE AND THE SECOND PRINTING AREA BEING RELATIVELY SMALL,THE BACK FACE OF THE PLATE HAVING AN INTEGRAL AREA IN RELIEFCORRESPONDING GENERALLY IN OUUTLINE TO AND APPROXIMATELY REGISTERINGWITH SAID FIRST RELATIVELY LARGE PRINTING AREA ON THE PRINTING FACE, THEAREA ON THE BACK FACE CORRESPONDING TO AND REGISTERING WITH THE SECONDRELATIVELY SMALL PRINTING AREA BEING GENERALLY FLAT WITH THE REMAINDEROF SAID BACK FACE.